Technical Field
Embodiments disclosed in this disclosure relate to an encapsulating glue film coating system, more particularly to an encapsulating glue film coating system and transfer roller thereof for encapsulating a substrate of a display device, and a method for coating the glue film.
Description of the Related Art
In the field of displays, Organic Light Emitting Diodes (OLEDs), and Active Matrix Organic Light Emitting Diodes (AMOLEDs) has been widely used in flat panel displays due to their characteristics of self-luminous, high contrast, fast response, small investment for manufacturing equipment, simple process, and the like. For example, the light-emitting principle of the OLED is that several layers of organic material (including an organic light emitting material) are deposited between two electrodes, and when a DC voltage is applied between the two electrodes, the organic light emitting material is caused to emit light.
In OLED displays, organic light-emitting material will fail in case of contacting with water and oxygen, therefore the glass substrate disposed in front of the organic light-emitting material should be encapsulated with a back cover plate, so as to be isolated from water vapor and oxygen, and thereby increasing life of a display. An OLED display is usually encapsulated with a metal cover plate, a glass cover plate or a film. A Metal cover plate is different from a glass cover plate in expansion coefficient, which leads to a deformation of entire display device and high cost. At present, usually glass cover plate is used. According to production process of an OLED, a plurality of recesses having a certain area and flat bottoms are required to be etched on the glass cover, with desiccant filled in the recesses, and at the same time, high-precision alignment marks are etched so that the display and the glass substrate can be precisely aligned and fitted.
Currently, in production process of such a glass cover plate, firstly, relative thick anti-etching protective films are applied on front and rear surfaces of a flat glass for forming a substrate, then one side of the glass is exposed to formed a pattern of the recesses, then developed to remove protective films inside the pattern, then the glass is disposed into an etching liquid to form the recesses, and finally the protective film on surface of the glass is removed. In this production process, a high-precision exposure machine is needed, otherwise the alignment accuracy does not meet the requirement for encapsulating, such that the manufacturing cost is very high; in particular, the adhesion between protective film and glass is inadequate, so that the film is easy to separate from the glass, resulting in a large number of defects, so that the production cost is further increased.
Further, due to requirement for high coating speed, the requirement for uniformity of coating on a surface is high, therefore there is needed a surface coating apparatus that can provide high-speed, high-uniformity coating and can precisely control of the amount of glue. Current drip type coating may provide a high coating speed, but the uniformity of glue is low, and a plurality of nozzles are needed, so that replacement of components is extremely time-consuming.